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PRESENTATIONPRESENTATION

ONON

SAFE CONSTRUCTIONALSAFE CONSTRUCTIONAL

PRACTICESPRACTICES

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Natural hazards: an overview

The main types ofnatural hazard that can pose serious risks to

the built environment are:

floods

earthquakes

tsunamis

landslides

volcanoes

fires

storms, and toxic environments

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Floods can occur:

following sudden rainfall or snowmelt

when rivers break their banks

as a result of surges in sea level

as a result of rising ground water

Building design options include

raising the building on plinth

relocating the building locally to higher ground raising the building on stilts

building strong columns and roof, but sacrificial walls that

are washed out in floods

clear openings on opposite sides of the building parallel to

the likely direction of water flood, such as under raised floors

strong corners and foundations to resist scouring, beamsbarriers to divert flows and debris

Support traditional risk management techniques where possible

as this can help identify safer areas that are less likely to suffer

from flooding.

Natural hazards: floods

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Earthquake resistant settlement planning should ensure that:

settlements are not located on alluvial plains, unstable soils,reclaimed land, unstable or steep slopes

buildings are spaced to avoid multiple collapse

Earthquake resistant building design should be appropriate to:

geographic location

economic group traditional construction

Design components may include:

a series of 3 ring beams per floor

through stones joining front and rear faces of rubble masonry

columns able to take tension and compression regular buttresses and dividing walls

continuous structural linkage between all building elements

fatigue stress is taken into account and effects monitored

square or rectilinear plans are used where possible

Natural hazards : earthquakes

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A tsunami is a large wave, or series of waves usually

caused by:

an earthquake

volcanic eruptions

underwater explosions or landslides

In tsunami prone areas site selection should ensure that

transitional settlements are located on high ground away fromthe sea.

The impact of tsunami on settlements and populations can be

mitigated through:

relocation of communities at risk identification of high ground for evacuation

identification of escape routes

reinforcement of flood defence systems including

through natural barriers such as reef, mangroves

and sandbanks

provision of Early Warning Systems

Natural hazards : tsunami

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The term landslide includes rock slides, rock falls, tree slides, mud

slides, debris flows, and avalanches

Past landslides should be assessed, including through consultation

with local communities

Landslides tend to occur on steep slopes or where land is

undercut by water

One indication of previous landslides is vegetation at a different

level of growth from surrounding areas

Factors which can increase the risk oflandslides:

deforestation

overgrazing

heavy rainfall

Foundation design can mitigateagainst the effect of landslides

Where possible settlements should

not be located in areas prone to

Landslides. Properly draining a site

can also prevent landslides

Natural hazards: landslides

less dangeroflandslides

damaging thesettlement

bend of river: risks of

water undercutting land,causing landslide

landslide risk to settlement

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Volcanoes produce various types of hazard:

hot ash and dust

mud and lava flows

fires

floods

landslides

rock slides

avalanches poisonous gases

tsunami

ballistics (rocks thrown into the air)

Settlements should not be located near volcanoes or lava flows

Settlement planning should include escape routes andcontingency plans

Building design should ensure that

large openings face away from the volcano

roof design allows for ash loading

Natural hazards: volcanoes

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Storm damage can be lessened by influencing the flow of wind

through the site, for example:

using wind barriers, such as trees and topography may

help to protect vulnerable shelters

the layout of buildings will effect how wind flows through the

settlement

the positioning of windows and openings in buildings can be

used to provide shelter as well as natural ventilation

Building design and retrofitting are measures that may include:

reducing overhangs, eves and gables

improving the strength of joints through the use of brackets

and cross bracing

introducing cross bracing and ties especially for wall platesand rafters

improving the fixing of roofing materials

introducing storm shutters for windows and openings

Natural hazards: storms

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The risk of fire is particularly high in dry areas where

forest fires or wildfires are common.

Also in cold or temperate climates where cooking and heatingstoves are used inside shelters.

Where possible methods formitigating risks from fire include:

fire alarms and fire doors which should open in the direction

of the escape

planning settlements to include fire breaks

providing water points and fire beaters forfire fighting

ensuring adequate fire escapes from buildings and fire drills

ensuring fire escapes are marked, clearand accessible

Natural hazards: fire

distance between

buildings should be

twice their height

the maximum travel distance to a

fire escape should not be more than

18m from any part of the building

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Local knowledge is critical for understanding toxic threats

and sources ofdangerous pollution

Toxic hazards may include:

contamination of surface or ground water

- arsenic

- chemical fertilisers or pesticides

- sewage

carbon monoxide and particulates emitted by vehicles,

generators or stoves

asbestos, this should be removed and its use avoided in

reconstruction

salt deposits from sea water flooding

human oranimal bodies

abandoned lead mines

depleted uranium weapons

Natural hazards: toxic environments

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Bibliography

Women, girls, boys and men(IASC 2006)

Handbook for the Protection of Internally DisplacedPersons (Global Protection Cluster Working Group,2007)

Transitional Settlement: Displaced Populations(Corsellis and Vitale, 2005)

Transitional settlement and reconstruction afternatural disasters (United Nations, 2008)